I believe that is intended to setup a special char device for doing 'extra' paravirtualization stuff. It's a communication path for doing copy-n-paste buffers and other things. The target_type=virtio ...
KVM, the Linux kernel hypervisor, is the up-and-coming enterprise virtualization contender. It’s lean, mean, fast, and runs unmodified guest operating systems with ease. In this crash course we’ll ...